Process of making cylinder packings



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Patented June Il, 1935 STATES- PATENTtIf-HCE.,

Paocnss VoF MAKING CYLINDER PACKINGS kPhilip W. Dempsey, Pittsburgh, Pa., assignor to The Westinghouse Air Brake Company, Wilmerding, Pa., a corporation of Pennsylvania Application October 28, 1933, Serial No. 695,638

7 Claims; o (c1. '1s- 55) method for making reinforced rubbery pistonl packing whereby thereinforcing fabric may be so built into the packing and the rubber compound sodistributed with respect to the fabric that the fabric is retained in its proper position and properly covered with rubber in order that the molding and curing operation. 1

Another object of the invention is-to provid ainethod of making a reinforced rubber packing having an annular peripheral corrugation, whereby multiple layers of reinforcing fabric may be properly built into the corrugated portion of the packing so that maximum flexibility, strength and resiliency may be obtained and so that the warp and woof strands ofthe reinforcing fabric throughout the corrugated and peripheral portion of the packing are diagonal to intersecting radii of the packing. This arrangement of the strands of the fabric provides maximum flexibility and resiliency at the peripheral sealing portion of the packing where the distortion the fabric will be completely enveloped during `thereof is maximum when the packing is pressed and. coniined within its cylinder.

A further object of the invention is to provide a method of and apparatus for making. a reinforced piston packing, whereby the materials of f forced packing, wherebyassembly of the material constituting the blank into a form approximating that of the inished packing is facilitated and whereby the molding operations are simy pliiied.

These and other objectsof the invention that will be made apparent throughout the further desciiptionthereof are attained by the method of and apparatus for forming piston packing hereinafter described and illustrated inthe ac companying drawings; wherein u prop er Fig-l is a plan view of the outer or convexv pressure face of a piston packingembodying features of my invention; L

Fig. 2 is a sectional view of the packing shown in Fig. 1 taken on the broken line 2-2 thereof;v

Figi-3 is an elevational view of afragment of the fabric reinforced rubber sheet strip used in building up the, blank such as is subsequently pressed andcuredto form the iinished packing;

Fig. 4 isasectional view of a mandrel or arbor upon which the blank is built up, showing'ma blank in a partial stage of formation; Y Fig. 5A is a fragmental'enlarged ysectional View of the `marginal portion of the blank showing the nature anddisposition `of the materials of a completed blank; f

Fig. 6 is an elevational View in reduced scale,

sure during the curing operation; o

Fig. 7 is a sectional view of a blankplaced within a mold section and with another mold section for conningvthe rcentral portion of' the blank in operative position;y

Fig`8 is a sectional view of the completed cured packing within the complete -mold and showing operating tools in position for separating the mold sections for. extraction of the nishedpack- Fig. 9 is a plan view of the mold and operating tools shown in Fig. 8;L and Fig. 10 isy a fragmental sectionalvi'ew of a dctail of the mold section interlock taken on the line IO-fl of Fig. 8. l

Referring to vthe drawings andparticularly'to Figs. 1 and2, wherein acompleted packing is disclosed, the packing disc comprises a central por'- tion I I having a central flat portion yI2 surround-l ed by.a portion I3 having a spherical surface or contour. which merges into an annular corrugation I4 that terminates in a peripheral or circumferential lip I5 that is'adapted to engage the, cylinder wall. j i

The lipportion -of the corrugation is nared outwardly at an angle from the cylindrical portion I6 of the corrugation and when the packing is mounted upon a piston,"not shown, such as disclosed in the above noted copending application; the lip portion I5 is compressed inwardly so that A y it is substantially'parallel with the wall portion I6 ci the corrugation, the material in the U-bend portion of the corrugation being then under pressure and tension, so that when the packing is in place within the cylinder, the resiliency of the material in theU-bend portion of the' corruga- As shown injig. ,2, the central portion Il of the packing` is reinforced byaflayer ofjwoven fabric IT whichmis embedded within the rubber compound and which terminates circumferentially at the point i8, a slight distance from the'` point at which the centrallportion- Hinergesintd the curved corrugated portion of. the packing.

As indicated in Fig. 2, the `curved vcorrugated'. portion of the packing is reinforcedby three 'layers of reinforcedmaterial, the inner layer i9 com-V prising a strip of fabric, such as is`shown in Fig. 3, so* disposed that the warp and Woof strands of the fabric, when the latter are in place withinthe packing, are diagonal to the intersecting radii throughout the v.circumference .of .the packing disc. The strip or band .I9' extends from'the peripheral lip .I of the packing inwardly s`o-..that it overlaps the marginal edge=of the fabric disc The centrallayer of fabric ZI-is similar to the layer j I9 and`- extendsV from' the' peripheral edge of Ythe packing inwardly-so that its'inner edge butts the peripheral edgeof the lfabricdisc Il, the-warp and woof strands oflthe fabricbcing'- disposed in the manner of the stripl I9. The outer layer 22' of the fabric isv similar to thestrip i9 and extends fromthe peripheral lip|5 inwardly so I that its inner `rnargin roverlapsthe v'pesame disc.

portion'of the packing be'extr'emely exiblfe'and resilient and have great strength. By reason'of the arrangement of the outer c three f layers;l of

fabric` so that thefwarpffand woof Ystrands theref` vare disposed diagonally gtojthe 'intersecting ra'- dii throughout the circumference of thegdiscfno strands of the fabricare" disposed' tangent to the curvature of the corrugation and,l therefore, iexibility isprovided every` directionin which the corrugation is normally distorted-inservice.` This would notl be the -case if the layerqo'f fabric l'l were extended toLthe peripheral lip'of-fthe packing, for in such case some strands of either the warp or woof would be tangent to the curvature of the corrugation and rigidity would result, which might Voccasion failureof thefpfoking under service condition.'y l I Itis also important that the central or spherical'portion of they packing vdiatriberelatively' rigid compared with thecorrugated flexible portion of thedisc, so that it 'will maintain its-,proper shape and adhere closely tothe piston uponwhich the packing is Vmounted and which is illustrated in the-above noted'copen'ding application.,` `vv d j y, The flattened portion l2 df the` packing disc ,is providedwithfour arcuate'stop lugs or, bosses 23, which are adapted'toengage the pressurehead of the cylinder and hold theymain body surface of the packing out `,offycontact with thepressure head, so that vit will notadhere thereto and so that viiuid under pressure .entering the cylinder;

may act upon substantially .the entiresurface of thepacking and flow freely to the (corrugated portion thereof.. 1

Y, 1` applied. As indicated in Figs. 1 vand2,thepor'tion of the' packing disc which .is.;rei'nforced v`.byl .thes'ev'eral layers `of fabric is of slightly greater thickness than the central portion Il', vand in order to insure that fluid under pressure will flow to the peripheral edge of the packing from the space within the arcuate bosses 23, spaces 24 are provided between the bosses 23 through which iiuid under pressure may iiow, and grooves`25 are'provided in;

the portion of increased thickness for permitting fluid 'under pressure to` iiow to theperipheral edgeof the packing inthe event that the bosses 23 are compressed suiiciently tol permit the portion ofincreased thickness to engage the pressure head' of, thejcylinder.

As indicated in Fig. 2, an annular bead 26 is provided on th'ewinner" face of the packing which is adapted to expand into an annular groove on the piston, not shown, for the purpose of retaining thepackingv upon thepiston as provided for in y the piston and packing structure disclosed in the aboveE noted copending application.

hepacking illustrated in Figs'land 2, is made by the following process.

Rubber compound is firstfrolled into a sheet` having the, desired thickness and then cut yinto strips having `the-general form shown in Fig. 3. Rubber compound is also rolled or frictioned `on to a sheet of'wide mesh cotton fabric, so that the layersof `rubberen opposite sidesof the fabric areunited `bythe rubber pressed into the interstices between the strands of the fabric, the thickness of the rubber compound coating ofthe fabric depending o n whether itis .used for'thecentral portion` of a blankor the peripheral portion, that forthelvcentral portion being relatively thick. The fabric' having the thinner coating is then cut into strips, suchas shown in Fig. 3, the warp and woof strands running diagonally ofthe strip. The fabric having the thicker coating is cut into the form of circular; discs. pared, have...a tacky., surface, so that :contacting The materials thusv preplaced.in ta. heated mold and pressed and curedy v into'a finish-ed packing. f

. The operation. ofbuildingup a blankis as follows.; VAcast metal mandrel or arbor 21, Figmi, is rotatably mounted upon a shaft 28 that is fixed to a support 129 which isv adapted to be securedto a work bench, not shown. The arbor is adapted to bev rotated bythe operator andthe blank receiving face thereof visshaped to conform. withthe' contour oftheouter or convex vface of the'blank, so that the blank formed thereon is given aldefinite shape that `will it readily into "the curing mold Whichwill hereinafter be described.` 1

In building .upza blank upon the arbor2'l,` the arbor is first coatedwith a ythin coating of la `composition which Will prevent permanent adherence of` the'- rubber materiali to. the blank.- A strip 3| of raw ,A or uncured rubber compound 'is then woundaboutgthe peripheral edge of the arbor as indicated in'Fig. 4. A second strip of raw rubber compound 32V is then wound or laid'upon the arbor so `thatthje outer edge thereof overlaps the inner edge of the strip 3 If, the strips being of such length thatvk the ends thereof slightly overlap when pressed upon the arbor.` A relatively narrow strip" 33,0f raw rubber compound is then wound upon the arbor and superimposed on the strip 3| for the purpose of. providing additional rubber stock ata point' adjacent the peripheral edges of the reinforced rubber compound -strips xto be later n'A fourth strip offraw rubber compound 34 is then wound upon the'f'mandreljsuperimposed on thestrips' 3| and 33 and slightly overlapping the' outer peripheral edge ofthe Astrip 32. The'structure is now ready to receive-a strip of reinforced rawV rubber compound 35 containing the fabric layer .|9, which is superimposed on thestript 34 and the strip 32 so that the outer peripheral edge 36:thereof slightly overlapsthe narrow strip`33 and the inner peripheral edge 31 thereof slightly overlaps the edge of the strip 32.

The reinforced rubber compound circular disc 38,Y having the Woven-fabric layer |1coated with a relatively thick layer of raw rubber compound on each side, is then pressed in placeupon Ythe arbor so that the peripheral edge '39 thereof overlaps the inner edge'v 31 of. the reinforced strip 35, care being taken to properlycenter the disc With respect to the inner edge of the strip 35. A second strip 4| of reinforced raw rubber compound containing the fabric layerv 2| is next Wound upon the arbor, so that it is superimposed on the reinforced strip 35 'and so that its inner edge 40 butts the peripheral edge 39 of theldisc 38 and so that the outer peripheral edge 53 thereof terminates just short-of the peripheral edge 36 of the rst reinforced disc 35. A'thirdand final reinforced strip 44 containing the fabric layer 22 is then Wound upon the arbor, sothat it is superimposed on the strip 4| and so that its outer peripheral edge 45 overlaps the .peripheral edge 43 of the second reinforced strip 4| and is substantially flush with the outer peripheral edge 35 of the first reinforced strip 35 and so that the inner peripheral edge 46 overlaps the peripherall edge 39 of the disc 38 and the inner edge 31 ofv .i the strip 35 as indicated in Figs. Ltand 5.

The exposed inner edge 46 of the third reinforced strip 44 is then coated with va rubber cement or liquid rubber compound` 5D,.so thatthe exposed fabric strands are covered with rubber, which will facilitate the flow of the raw rubber compound thereover during the pressing and cur` ing operations to be hereinafter described. The peripheral marginal portions of the rubber compound strips 3| and 34 are next folded over the peripheral edges of the reinforced strips in the manner shown in Fig. 5, to provide an abundant quantity of raw rubber compound stock at rthe peripheral margin of the blank.

The arbor with the blankl adhering thereto is then removed. from the shaft 28 and placed on phere of the room in which the blank Was formed for the purpose of permitting volatile liquids contained Within the rubber cement and the raw the packing is cured comprises a base section 5|. having a concave mold surface 52 having the contour of the outer convex face' of the finished s packing. The mold section 5| is provided with an annular ridge 53 Which serves to form the U-bend portion or corrugation of the packing and arcuate grooves 18 for forming thearcuate bosses 23 on the finished packing. The mold also comprises a central section 54 having a convexmold surface 55 having the contour of the central portion of the-inner: concave face of the packing. fThe vsection-54 is provided with a frusto-conical boss ,55 which serves. .as a centering guide for an annular mold section-51, which constitutes :the third section. of vthe mold `andvvhichiis adapted tomake metal. 'to-metal contactwith anannular surface 58 ofthe section 454 and arf annularsurface' 59v on.`

the mold section 5|. An annular .flange'fii` on the inold section. 5| serves also to center the annular mold section51 and when the threemOId'sectiOns are in.. assembled relation, a space is provided-be; tween the combined 'mold-sections having the exact contourofrthenished packing.

- Because of the presence of the annular ridge r53 forforming the corrugationrwhich prevents gases from'owing past it, 'itis necessaryto provide means throughv which'the gases may .be Vvented from :the central. portion ofjlthe outer face vTof. the'packing.` The mold section 5| is therefore provided Witha .central bore. 62 l that is closed by aplug'53 that closely Yfits Withiny thebore," the clearance between the mold sectionT andthe plug, however-being suiicient-to permit gasesto. i

escape to thev atmosphere through the bore`= 62.-"4 Theplug isprovided with an annular groove 63 for receiving` any excess material flowing through saidiclearancespace.- l s' The moldsection-51is provided Withannular grooves 54 and 65, which cooperate respectively with's'annul'ar groove V65 in the mold ,section 5| and'annular groove=61 inr the face 58'of the moldl section v54, which grooves constitute overow grooves for-the excess material and which function in the manner disclosed in my PatentNo.A

`1,910,525, issuedMay 23, 1933.` Gases'. generated within Ythe moldduring operation may also escape to the atmosphere through the said grooves and from the space between the contacting surfaces of themold section. The vcentral mold sectiony 54 is prvided'lwith a recess vorfbore B8 which is threadedfor receive"v ing ascrew plug having a key vhbleslot-'il therein for receiving a key-lug 12 having Wings 13 thereon adapted `to engagearcuate cams-p14 which are provided with inclined lcam surfaces,- Which are adapted to engage the wings 13 ofv the key lug 12 when the operating handle 15 is turned through vsubstantially 45.l The v operating handle 15 is provided with Wings 16 'that extend over-the annular mold section 51 and when the key lug 12 is inoperative engagement with the arcuate cams 14,5the central mold section 54fis drawn `into close engagement with the annular mold section 51, so that the mold sections 54 and 51- are connected in order that they rnayl be handled as avunit when it is desired to separate the'mold sections 54" and 51 fromthe mold sec-` tion 5| for the'purpose of removing a'fini'shed packing and inserting a blank. The operating handle 15 maybe readily detached'from the mold sections 54r and 51'by turning the operatingv handle sothat the lugs 13 register with -theykey slot 1|, at .which time/the operating handle may` be withdrawn. fi The'fnalwmolding and curingoperation consists in .placing round strips orbars of *raw rubber Acompound inf the grooves 10' toformthe bosses 23 on thev iinishedipacking, yplacing the blankwithin the" mold section 5|V as shownin Fig. 1, placing the central mold section v54 in position upon the central portion of theA blank and' then in placing the annular mold section 51 in assembled cooperating fpositionl upon the mold section 5| and the mold section 54. The assem` bled mold is .thenplaced inranhydraulic press,- such :astis disclo'sed'in Fig. 6 andwhichiisof well known .construction and.. comprises 'a'base cylinder 8l containing an i hydraulic ramV or plungerA 82 and. whichv-supports:.vertical guides 83 to which'a stopheadf84. is.AA attached. iflThe' plunger 82` is provdedfwith'a pressure :fhea'dy 85 and oating Vplatens rare 'mounted' within... the

guides 83 `where they arelsupportedfor vertical l movement.V The pressure. head 185 v1 and'. the lstop head 84? andthe platens'fll are-hollow. and the chambers therein are supplied with." steam through pipes 81 `ata-pressure of. approximately fifty pounds per square inch,zf`or maintaining the temperature of the.- elements Ikof the pr'ess atsa temperature ofVl approximately 300 Fahrenheit; Assembled moldsfcontaining the; blanks are placed betweencthe' said heads and the platens and between theplatens asaindicated .in';.Fig.z.6. Hydraulic pressure of k.many tonsr is ;'then.applied to the plunger-82 and -thegmolds andthe .blanks contained therein; are subjected to great pressure and heated .through themedium-of said heads.; and platensffor 'af period .approximating fty minutes, during which time thecuring of the raw rubber compoundis completed.

After the curing operationhasbeencompleted, the hydraulic pressure is releasedfromnthe plunger-82 and the. platens are permitted to separate. The molds arethen Withdrawn from the' press andplaced--upona table. f A forked` tool 88 `having lugs 89 is then inserted in the annular groove. 9 I `-between anges ofvv the-mold sections5| yand 5l. and the lugs 89 are turned by;` the tool to slightly i separate the mold sections 5|, and. 5".I The op eratinghandle 1,5 is then connected-td. the cen-v trai sectionn, so that the mold sections 54`and l ereonnectedf-b The, operatnsltool 88. is then` moved to again pry the moldsectionsl and v51 apart, Carrying theentral. moldsectonl .with

the mold-section 5l. 'I heiinished` packing ad- .nular bead 26' and is withdrawn from the mold Section 5|# The operating handle.- '(5is3then removed and the" annular mold section 5'l.i s then separated from the lmold section 55. 'corrugation Vof the finished packing then projects ,abovethe upper face ofy the central moldsection 54, vpermitting the operator togripthe corrugationand strip the packingfrom the mold section 54., 'Ihe packing `is fthen completed, except ,that it lcon-v tains a slight flash at the 4points offjoinderpfv the imold sections, which'ash is trimmed from the packing byf any preferred Ymeans suchasby shearing.

f I ackings made under abovejspeciiied .proc-4r ess are consistently uniform in e shape and dimenf` sions' and the"reinforcingfabric is lcompletely embedded within the"rubber ,co r'rfp,ound, so'that no portionthereof isexposed. Thefcorrugated annular portion of the pack and resilient."

While but one method and "but `Aone Amold con# struction is shown for making a pistonpacking,

itis; obviousf that changesjma-y 4be-A made in the method .and the mold construction fwithout de' parting fromthe spiritA of thelinventionand'that While the piston packing,disclosed vis for packing' a piston, vthe pekine-.fprocesslmay be employed for making. ,other packingfwhere it is ,desirable to have'arlexible peripheralportiom claim as. newand esire. Patent ist.

. 1. 1The'method-of. forming Ya resilient-packing' disc which consistsin-c'zoatingv reinforcing fabric with raw,A plastic, curablesubstance, forming a circular disc from'someof said material, forminga. plurality ofV annuluses vfrom'm'ore of said material,"';oining the innerfmarginof .said annuluses'to the margin iofvsaid disc in overlapping relationship to form a blank, confining said blank underl pressure -so`as -Atofgive it its-,final form 'and in applying heatto saidblank while so conned ,lforsfcuringv it intoa resilient one-piece packing.

.2. The method offforming a resilient packing disc which .consistsin coating strandsof fibre disposed g atan `angle to one. another with. av raw,

plastic`,;adhesive; curablejsubstance, forming. a

circulardisc from some o isaid material, vforming annuluses fromjother of .sai'dlmaterial sothat said strands are nonftang'ential to the' curvature of said annulns,` joining .the inner .marginsrof said annuluses tothe'margin of saidV disc by overlapping said-margins and pressing. them. together so that they 'adhereitoform a blank, conning said blanklunderzpressure so asto give it itsfinal llorm and., in applyingheatto 'said blank for curing it into a resilient one-piecepacking.

3. The method .ofiorming aresilient packing discbhaving a' peripheral annular corr'ugation which` consistsincoating reinforcingl strands of bre with a raw, plastic, adhesive,.curable substance such as rubber toform a atsheet thereof, forminga circular disc from some of said mate# rial, formingthree annuluses from more' of said which consists in'icoating reinforcing fabricwith raw rubber, forming a circularldisc from some of said material, forming annuluses from other of said materiaLLjoining"said-'Tdisc and lsaidannu. luses by placing arrannulus .'onoppositesides of the disc withzthey inner margins of the annuluses overlapping. the '.marginv of lthe 1 disc;` covering the outer marginal edges of-saidfannuluse's with raw- .rubben confining the blank s'o'formed under pressure withina moldhaving thefinal contourof the' packing, an'din heating 'said mold lfor curing said rubber when the blankiisy so conned for arnalgfa` mating said discandzannuluse'sfinto aone-`piece packing. y .4

5.'A 'I'he method of forming 'a rubber packing disc which consists in coating. reinforcingv fabric'with raw rubber, forming a" circular disc'from some of saidlmaterial, formin'gannulusesfrom more of said' material, coating f the' margins 'of said I disc and annuluses with a :rubber cement material,

. joining said discland said annuluses by vplacingan inner margins of, the a n1 "i u l1,ises f overlapping the 'margin of the' disc, subjecting the Ablank thus formed to a drying atmosphere `until the Vcement has dried,v then conning the blank under pressure within afm'oldv ,hatngitnennn contour, ,orme packing and in heating said mold for curing said rubber when the blank is4 s o conned for amalga-i mating4 said disc-and annuluses into a onepiece 6. The method of forming a rubber packing disc which consists in coating reinforcing fabric with raw, tacky rubber, forming a circular disc from some of said material, forming stripsfrom more of said material, forming raw, tacky rubber in sheet form, forming strips of sheet rubber, then forming a blank by laying one or more strips of raw rubber on the marginal edge of a circular retaining suriace having the contour of the outer surface of the blank being formed, superimposing a strip of said material over the inner portion of said strips of raw rubber, placing said disc on the retaining surface with its margin overlapping the inner margin of said strips of material, laying a second strip of said material on the rst strip so that its inner edge butts the marginal edge of said disc, laying a third strip of said material on the second strip of material with its inner margin overlapping the margin of said disc, then folding the outer portion of said strips of raw rubber over the outer margins of said strips of material, removing the blank from said retaining surface, conning the blank in a mold having the contour of the finished packing and in heating said mold f material, forming said strips into annuluses, plac? ing one of said annuluses in butt relation to the marginal edge of said disc, joining said disc and annulus by superimposing said other annuluses on opposite sides of the first said annulus so that their inner edges overlap the margin of said disc, and conning the blank so formed in a mold having the iinal contour of the packing under pressure and in heating said mold for curing said rubber while the blank is so conned for amalgamating said disc and annuluses into a one-piece 20 packing.

PHILIP W. DEM'PSEY. 

